Carburetor



Jan. 17, 1939. P. x. A. GISTUCCI CARBURETOR Filed May ll, 1936 2 Sheets-Sheet 2 H. w 7 $4 4 T 5 mm m W 9 z 6 75 whi w v m T L i U 5J5 6 W Q Qfiw A TTORNEK Patented Jan.- 17, 1939 UNITED STATES 2,144,011 PATENT OFFICE? CARBUBE'I'OB Paul Xavier Auguste Gistucci, Paris, France, as-

signor to Societe Generale des Oarburateurs Zenith, Levallois-Perret, France, a corporation of Switzerland Application Mayll, 193s, set-n1 No. 78,991, f In Belgium May it, 1935 a 9 Claims. (01. 26149) existing in the induction passage of the c'ar-' buretor. The connection between said membrane and said valve issuch that the valve is closed when the motor is inoperative and the depression is zero, and open when the membrane is actuated by the depression created by the motor while in operation.

Such arrangements are necessary when the fuel is supplied to the motor under a certain pres-- sure, in order to avoid the continuation of fuel flow into the motor when the same stops.

A difficulty in providing a practical arrangement of this type lies in the fact that the'depression created by the motor drops to a very low value during acceleration, hence it is necessary that the arrangement be sufliciently sensitive to enable this very weak depression to maintain the' fuel valve open, since otherwise the valve will close and interrupt the supply of fuel to the motor.

Viel U. S. Patent 1,955,037, dated April 1'7, 1934, 'and assigned to the assignee of the instant application, discloses an arrangement designed to give such mechanism great sensitivity. In

said arrangement the membrane located in the wall of the fuel chamber is of small dimensions and is connected to the movable wall of a chamber to which is transmitted the depression created by the motor. This movable wall is of large dimensions in comparison to the membrane,. so that the effect of the depression on this membrane is multiplied and the mechanism is thereby rendered very sensitive to slight depressions. ment is satisfactory when the same is placed in a fuel line in which the pressure is low; for instance, if it is placed in a linereceiving fuel through a pressure regulator which supplies the fuel under a pressure of approximately 10 to 20 grams per square centimeter. But such an arrangement cannot be placed in a fuel line supplied directly by a fuel pump of the usual type which creates a pressure around 300 grams per square centimeter, since such pressure acting on the membrane would exert on the same, in spite of its small dimensions, a considerable force, and it would be necessary to make the movable wall subject to the depression,of a size altogether impractical in order that a weak depression would be sufficient to operate the mechanism.

' An object of the present invention is to proated by the depression.

The operation of such an arrangevide a fuel shut-off arrangement, theoperation of which is not affected by variations in the pressure of the fuel, and the dimensions of which are smaller than the dimensions of mechanisms of known types. a V

In accordance with the present invention an additional membrane is placed in the wall of the fuel chamber and is connected to the membrane actuated by the depression in such a manner that the pressure exerted by the fuel on the additional membrane effectively balances the pressure exerted by the fuel on the membrane actu- Under these conditions the fuel exerts on the assembly of membranes'a resultant force which is actually zero no matter what the pressure of the fuel, and a very slight depression suflices to operate the mechanism even if the same is placed in a fuel line inwhich the pressure is Obviously, the single membrane actuated by the depression may be replaced by several membranes actuated by the depression. Similarly,

- the single additional membrane may be replaced by several additional membranes. In such case the various membranes will be interconnected in such a manner that the assembly of the membranes constitutes a system of membranes under substantially balanced pressures. The fuel exerts on each membrane a predetermined pressure which is equal to the product of the efiective area of the membrane by the fuel pressure The term system of membranes under balanced pressures is intended to include a system in which the membranes are interconnected in such a manner thatthe total of pressures exerted by a system of balanced forces. If the balance is obtained under a given fuel pressure, it will obviously be maintained at all pressures, since the forces acting on the different membranes will vary proportionately to the pressure. The design of a membrane system under balanced pressures is an elementary problem, which may be readily solved, and such a system constitutes an arrangement clearly defined.

The effective area of a membrane is the ratio the fuel on the difierent membranes constitutes of the total pressure exerted by the fluid on that membrane to the unit pressure of the fluid. The

ated by the depression created'by the motor may be subjected either directly to such depression, or may be connected to the movable wall of a chamber which is subjected to such depression, in a' manner similar to the arrangement described in Viel Patent No. 1,955,037, heretofore mentioned. If a throttle valve is mounted in the induction passage of the motor it will be preferable to utilize the depression existing posterior to the throttle valve.

The additional membrane or membranes may be subjected to the atmospheric pressure or to the pressure existing at the motor air intake. When the motor is supplied with air from a supercharger, this membrane or membranes may be subjected to the pressure existing at the supercharger air outlet.

The fuel valve is preferably placed in such a manner that it opens against the direction of fuel flow, since such "an arrangement increases the sensitivity of the mechanism, as.will be apparent hereinafter.

Preferably a spring tends to close the fuel valve.

In a preferred embodiment of the invention, the membrane actuated by the depression and the additional membrane are parallel and are connected by their centers, and both have the same effective areas.

The following description, and the attached drawings, are given as anexample for better understanding of the way in which the invention may be applied.

Figure 1 shows schematically in. longitudinal section a carburetor provided with an arrangement embodying the" invention.

Figures 2, 3 and 4 show schematically in longitudinal section modifications of the arrangement shown in Figure 1 which differ from the same by the arrangement of the fuel valve.

Figure 5 shows schematically in longitudinal section a further modification of the arrangement shown in Figure 1 in which the membrane actuated by the depression is not directly subjected to it.

Figure 6 shows schematically in longitudinal section a modification of the arrangement shown in Figure 1 but difiering therefrom in the arrangement of the membranes.

The carburetor shown in Figure 1 comprises an induction passage I supplied with air through air intake 2, and controlled by a throttle valve 3.

The induction passage receives fuel from a. fuel outlet 4, which is controlled by a needle 5, and discharges posterior to the throttle valve 3. The movements of needle 5 are mechanically controlled by the movements of throttle valve 3 by means of a lever 6 fixed to the throttle valve shaft, connecting linkl, and lever 8 pivoted at 9. I The fuel outlet 4 is supplied with fuel under pressure througha conduit III-which receives fuel from a fuel pump-of the usual type .or from a headed reservoir (not shown). The arrows indicate the direction of fuel flow. A pressure regulator II of any suitable type may be placed in conduit II! in such a manner as to reduce the pressure of the "fuel supplied to the fuel outlet 4 to a predetermined value which may, for example,

be around 10 to 20 grams per square centimeter,

whereas the pressure in conduit 10 is usually around 300 grams per square centimeter if the conduit is supplied'by a pump. The pressure regulator II may be omitted, if desired.

A valve I2 is located in conduit I0, and a fuel chamber I3 communicates with said conduit. The walls of chamber I3 comprise membranes I4 and I5 which are parallel and have the same effective area. The two membranes are connected at their centers by means of rod I6. Membranes I4 and I5 may be formed of fabric discs impregnated with a substance rendering them impervious and provided at their central portions with metallic discs I! and I8. These fabric discs are formed, as known in the art,.in such away as to permit them to follow slight displacements in either direction from their median position. Membranes made in this manner possess very negligible stiffness, so that their displacement does not require any appreciable force. Membranes I4 and I5 are connected to valve I2 by' lever I9. Lever I9 is pivoted at 20, and one of its ends 2 I is engaged between two flanges of rod I6, while its opposite end I3 is engaged by flanges of stem 14 which is fixed to valve I2 and guided in a recess I5.

Membrane I4 separates the fuel chamber I3 the throttle valve 3. In chamber 22 is located a rod 24 which serves as a stop for membrane I4. A spring 25 placed around rod 24 tends to repel membrane I4 from this rod. This spring may, however, be omitted.

Membrane I5 separates fuel chamber I3 from a chamber 26 which, in the case of a carburetor supplied with air by a supercharger, communicates through passage 2I with air intake 2. The air intake 2 communicates with the supercharger outlet so that the pressure existing at the supercharger outlet is transmitted to chamber 25 and membrane I5. When the carburetor is not provided with a supercharger, chamber 26 may be omitted and membrane I5 is then exposed directly to the atmosphere.

The, operation of the device shown in Figure 1 is as follows:

, Since the two membranes I4 and I5 have the same effective area, the forces exerted by the fuel pressure on these membranes are actually equal and balance each other through rod I'B which connects the centers of the two membranes.

When the motor stops, valve I2 is held against its seat by the fuel pressure in chamber I3 and also by spring 25, the pressure of which is transmitted to valve I2 by rod I6 and lever I9. The purpose of spring 25 is merely to assure the closing of valve I2 in case the pressure in chamber I3 is insufficient. This spring may be very light.

When the motor is started, throttle valve 3 being closed, the operation of the motor creates a depression in" the induction passage I, and this depression is transmitted to chamber 22 and membrane I4. Under the effect of this depression, membrane I4 is displaced toward rod 24 against the pressure of spring 25 and against the pressureexerted by the fuel on valve I2. Membrane I4 carries with it membrane I5 and lever I9, thereby opening valve I2. The displacement of the membranes is limited by contact of rod 24 'with membrane I4. I

Once the valve I2 is open, the fuel outlet 4 is supplied with fuel and the motor operates in the usual manner. The seat of valve I2 is sufficiently large that the pressures existing in passage III on either side of the valve are practically the same when the valve is open, so that during nor- -mal operation the valve 'is-su'bjecte'd only to a to overcome the pressure of spring 25 is sufficient to keep thevalve open by acting on membrane I4. Since the spring may be selected as weak as desired and can even be omitted, it is obvious that a very light depression is capable of wise, the membranes may be disposed vertically so that the weight of the liquid will have no influence whatever when the mechanism is in normal position.

It was stated above that the two membranes I4 and I5 have the same effective area. In practice, two identical membranes I4 and I5 may be used, but it should be noted that the effective area of a membrane is not absolutely constant and that it varies slightly when the membrane is displaced one way or other from its median position. Actually the displacements of membrances I4 and I5 are very slight and the resulting variations in the, effective areas of membrances I4 and I5 due to these displacements are negligible and do not -interfere with the functioning of the mechanism.

Insteadof making the effective areas of membrances I4 and I5 equal in order to form a balanced membrane system, one may make them slightly different so that the system comprising these membranes and valve I2 will be in balance when the valve is closed. In this manner the force necessary to open the valve during starting is reduced. Since-the size of valve I2 is small in comparison to membranes I4 and I5 the difference between the effective areas of the membranes which is required to fulfill this condition is slight, so that membranes I4 and. I5 may in fact be considered as a system of balanced pressures. Furthermore, the effective area of membrane I5 may be made slightly larger than that of membrane I4 in order to increase the force tending to close valve I2. However, such slight variations in the effective areas of the membranes do not affect the essence of the invention.

In the foregoing description the depression existing in the induction passage I and transmitted to membrane I4 was discussed. When the air intake 2 is supplied by a supercharger, the pressure existing in the induction passage may be higher than the atmospheric pressure, so that, properly speaking, there is no depression in this passage relative to the atmospheric pressure. However, the motor causes a depression relative to the pressure existing in air intake 2, the carburetor being operated by said depression. Conforming to general usage, the term depression is used herein in a general sense both in case of supercharged motors and motors supplied with air at atmospheric pressure.

In the arrangement shown in Figure 2, the fuel supply conduit is designated by reference numeral 28, and the arrangementis such that the fuel pressure tends to open valve I2, whereas in the arrangement shown in Figure 1 the fuel pressure tends to close this valve. Spring 29 of Figure 2, which corresponds to spring 25 of Figure 1, must be sufliciently strong to maintain valve I2 closed against the fuel feeding pressure when the motor is inoperative. During normal operation a greater depression will-be required to maintain valve I2 open, since spring 29 of Figure 2 is stronger than spring 25 of Figure 1.

In Figure 3 valve 30, corresponding to valve I2 inthe arrangement shown-in Figures 1 and 2, is placed in the fuel supply conduit 3I and opens outwardly of chamber I3, whereas in the arrangements shown in Figures 1 and 2 valve I2 opens inwardly of chamber I3. Furthermore, the fuel pressure tends to close valve 30, consequently spring 32 may be made very weak. During normal operation a very slight depression will be sufficient to maintain valve 39 open.

In the arrangement shownin Figure 4, valve 30 in the fuel supply conduit 33 also opens outwardly of chamber I3, but the fuel pressure tends to open this valve. Spring 34 obviously will have to be stronger than spring 32 in Figure 3, because it must be able to keep valve 39 closed against the fuel pressure. Consequently during normal operation a greater depression will be required to maintain the valve open than in the arrangement shown in Figure 3.

Comparing the operation of the arrangements shown in Figures 1 and 4, it is evident that it is of 'very little importance whether the fuel valve opens inwardly or outwardly of the fuel chamber. The direction of the valve opening relative to the fuel flow direction, however, is important. Preferably the valve should be located in such a. manner as to open against the direction of the fuel flow (Figures 1 and 3).. The depression required to maintain the valve open during normal operation is consequently slighter and the mechanism is more sensitive. The placing of the valve so that the same opens against the direction of fuel flow constitutes a preferred feature of the present invention.

In the arrangement shown in Figure 5 a valve 35 is placed in the fuel supply conduit 35. A fuel chamber 3'! communicates "with conduit 36. The walls of the fuel chamber comprise two membranes 38 and 39 having equal effective areas, their centers being connected by a rod 40. The rod 40 is connected to valve 35 by means of a lever 4| pivoted on axis 42. Membrane 38 also separates the fuel chamber 31 from a-chamber 43. A rod 5I extends into chamber 43 and serves as a stop for membrane 38. Around rod 5| is mounted a spring 52 which tends to repel membrane 38 from-rod 5|. Membrane 39 separates the fuel chamber 31 from a chamber 44. Chambers 43 and 44 communicate with a conduit 45 which in turn communicates with the carburetor air intake 2. These two chambers may if desired communicate with the atmosphere.

Chamber 44 comprises a movable wallconsisting of membrane 46 which may, however, be replaced by a piston. Membrane 46 separates chamber 44 from a depression chamber 4'! which communicates though passage 48 with the induction passage I. Membrane 46 is connected to membrane 39 by means of lever 49 pivoted at 50. Ihe two arms of lever 49 may be made of unequal length when the motor is started, the depression transmitted to membrane 45 acts through lever 49,

rod 40, and lever 4|, to open valve '35 against 'the fuel pressure acting on valve and against the pressure of spring 52.

Since the pressure acts on-membrane inbranes 38 and 39 which enclose the fuel chamber may be made very small. In practice it is sufficient to make these dimensions such as to per- 59 which is pivoted at 69.

mit'the necessary displacement of valve 35 without rendering the membranes so stiff as to cause a considerable resistance to their displacement. By making the membranes 39 and 39 of reduced dimensions the importance of slight dilleren'ces between the effective areas of membranes 38 and 39 is diminished. This arrangement is advantageous in cases where the fuel supply pressure is very highl I The invention obviously is not limited to any particular arrangement of membranes or to any particular arrangement of mechanical connections between the different membranesandthe valve.

In the arrangement shown in Figure 6, a valve 53 is placed in the fuel supply conduit 54. This valve is fixed to a sleeve 55 slidably guided in cylinder 55, and is perforated by ports 51 which permit the free passage of fuel. A spring 58 acts on the valve and tends to hold the same against itsseat.

A fuel chamber 59 communicates with fuel conduit 54, and comprises movable walls formed by membranes 99 and GI. Membrane 59 separates the fuel chamber 59 from a chamber 62 communicating through passage 63 with the motor induction passage. Membrane 6| separates thefuel chamber 59 from a chamber 54 whichcomm unicates through passage 65 with the atmosphere or the air intake.

A rod 65 passing through a guide incorporated inthe wall of chamber 62 extends between the center of membrane 50 and the end 61 of a lever Similarly, a rod I9 extends between the center of membrane 5| and the end ll of lever'68. The fuel pressure acting on the membranes and 6| maintains rods and 19 in contact with lever 68. arms a and b of lever 68 are of lengths inversely proportional to the corresponding effective areas 7 of the membranes, so that membranes 60 and SI and lever 68 form a system of balanced pressures. Valve 53 carries an extension 12, the end of which contacts with the center of membrane When the motor stops, spring 58 maintains the valve 53 closed. During the operation of themotor, this valve is maintained open against the pressure of spring 58 by the depression acting on membrane 50, the movements of which are transmitted to membrane BI and valve 53 by lever 68. It will be noted that the arrangement of Figure 6 comprises two unequal membranes having no positive mechanical connections with each other, the contact between the different parts being effected by the fuel pressure or by a spring. a

The invention obviously is not confined to any one type ofcarburetor. The drawings disclose a carburetor of the anterior throttle type, since it is chiefly in this type of carburetor that the The two fuel outlet is supplied under a positive pressure,- but the invention is obviously applicable in connection with any. typeof carburetor and particularly posterior throttle carburetors of the usual type. The invention is also applicable where the fuel is not supplied to the motor by a carburetor, properly speaking, but is supplied to the immediate vicinity of the inlet ports, or is injected directly into the motor cylinders.

I claim:

1. A fuel shutofl mechanism for internal combustion motors comprising a valve located in the motor fuel supply conduit, .a membrane located in the wall of a fuel chamber communicating with the fuel conduit and controlled by the de-- pression existing in the motor induction-passage, and a connection between said membrane and said valve arranged in such a manner as to cause the opening of the valve when said membrane is actuated by the depression created by the mo- ,tor during its operation; characterized by an additional membrane located, in the wall of the fuel chamber and connected to said membrane controlled by the depression, said connection being such that the pressure exerted by the fuel' on said additional membrane effectively counterbalances the pressure exerted by the fuel on said membrane controlled by the depression.

2. An arrangement as specified in claim 1, characterized by the said membrane actuated by the depression being subjected directly to the motor depression. 7

3. An arrangement as specified in claim 1, characterized by the said membrane actuated by the depression being connected to a movable wall of a depression chamber which communicates with the induction passage of the motor.

4. An arrangement as specified, in claim 1, characterized by the fuel valve opening against the direction of fuel flow.

5. An arrangement as specified in claim 1, characterized by a spring tending to close the fuel valve.

6. An arrangement as specified in claim 1, characterized by the valve closing being 8on- -trolled by the depression existing posterior to a throttle valve located in the motor induction passage.

'7. An arrangement as specified in claim .1, characterized by the said additional membrane,

being subjected to the pressure of the motor air intake.

8. An'arrangement as specified in claim 1, characterized by the membrane controlled by the depression and the additional membrane being parallel, having equal effective areas and be- 'a fuel line supplying said fuel chamber, a valve controlling the inflow of fuel to said chamber,

means for subjecting one of said movable walls to the pressures in the induction passage posterior to the throttle, means for subjecting the other of said movable walls to said superatmospheric pressure, and an actuating connection between said movable wallsand said valve.

PAUL XAVIER AUGUSTE GIST-UCCI. 

